An image forming method for forming an image by ejecting an ink on clothes such as a T-shirt and a bathing suit by an ink-jet method has been known. However, the image forming method causes bleeding of the ink on the surface of the cloth of the clothes, impregnating of the ink into the cloth, which result in a problem in image formation. As a method for solving this problem, a pretreatment method in which a pretreatment agent is adhered to a cloth prior to image formation on the cloth in order to suppress the bleeding of an ink on the surface of the cloth and the impregnating of an ink into the cloth has been proposed.